Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.61	3.741%	$116.8227	$116.82	$116.80	$116.80
Purchase #2	$78.57	5.816%	$83.1396	$83.14	$83.15	$83.10
Purchase #3	$183.78	6.443%	$195.6209	$195.62	$195.60	$195.60
Purchase #4	$105.42	4.866%	$110.5497	$110.55	$110.55	$110.50
Purchase #5	$112.52	11.658%	$125.6376	$125.64	$125.65	$125.60
Purchase #6	$28.27	12.701%	$31.8606	$31.86	$31.85	$31.90
Purchase #7	$32.38	3.723%	$33.5855	$33.59	$33.60	$33.60
7 purchase totals =	$653.55		$697.2166	$697.22	$697.20	$697.10